fixed types for mapbox/wellknown (#41424)

* fixed types for mapbox/wellknown

* added author, added null return type and test

* added null to $ExpectType return type

* fixed tests

types/wellknown/index.d.ts

@@ -1,7 +1,35 @@
 // Type definitions for wellknown 0.5
 // Project: https://github.com/mapbox/wellknown#readme
-// Definitions by: Yair Tawil <https://github.com/yairtawil>
+// Definitions by: Davide Scalzo <https://github.com/davodesign84>
+//                 Yair Tawil <https://github.com/yairtawil>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 
-export function parse(input: string): {};
-export function stringify(gj: {}): string;
+export type GeoJSONPosition = [number, number] | [number, number, number];
+
+export interface Geometry<T, C> {
+    type: T;
+    coordinates: C;
+}
+
+export type GeoJSONPoint = Geometry<"Point", GeoJSONPosition>;
+export type GeoJSONMultiPoint = Geometry<"MultiPoint", GeoJSONPosition[]>;
+
+export type GeoJSONLineString = Geometry<"LineString", GeoJSONPosition[]>;
+
+export type GeoJSONMultiLineString = Geometry<"MultiLineString", GeoJSONPosition[][]>;
+
+export type GeoJSONPolygon = Geometry<"Polygon", GeoJSONPosition[][]>;
+
+export type GeoJSONMultiPolygon = Geometry<"MultiPolygon", GeoJSONPosition[][][]>;
+
+export type GeoJSONGeometry =
+    | GeoJSONPoint
+    | GeoJSONMultiPoint
+    | GeoJSONLineString
+    | GeoJSONMultiLineString
+    | GeoJSONPolygon
+    | GeoJSONMultiPolygon
+    | null;
+
+export function parse(input: string): GeoJSONGeometry;
+export function stringify(gj: GeoJSONGeometry): string;

types/wellknown/tslint.json

@@ -1 +1,3 @@
-{ "extends": "dtslint/dt.json" }
+{
+    "extends": "dtslint/dt.json"
+}

types/wellknown/wellknown-tests.ts

@@ -1,7 +1,10 @@
 import * as wellknown from 'wellknown';
-wellknown.parse("POINT(1 2)");
-const geoJson: {} = {
+
+wellknown.parse("POINT(1 2)"); // $ExpectType GeoJSONGeometry
+
+const geoJson: wellknown.GeoJSONGeometry = {
     coordinates: [1, 2],
     type: "Point"
 };
-wellknown.stringify(geoJson);
+
+wellknown.stringify(geoJson); // $ExpectType string